Inhibitory mechanism of 17ß-aminoestrogens in the formation of Aß aggregates.

ABSTRACT

Alzheimer's disease (AD) is a complex neurodegenerative disorder associated with the aggregation of the amyloid-beta peptide (Aß) into large oligomers and fibrils that damage healthy brain cells. The predominant peptide fragments in the plaques are mainly formed by the Aß1-40 and Aß1-42 peptides, albeit the eleven-residue Aß25-35 segment is largely used in biological studies because it retains the neurotoxic properties of the longer Aß peptides. Recent studies indicate that treatment with therapeutic steroid hormones reduces the progress of the disease in AD models. Particularly, treatment with 17ß-aminoestrogens (AEs) has shown a significant alleviation of the AD development by inhibiting oxidative stress and neuronal death. Yet, the mechanism by which the AE molecules exhibit their beneficial effects remains speculative. To shed light into the molecular mechanism of inhibition of the AD development by AEs, we investigated the possibility of direct interaction with the Aß25-35 peptide. First, we calculate various interacting electronic properties of three AE derivatives as follows prolame, butolame, and pentolame by performing DFT calculations. To account for the polymorphic nature of the Aß aggregates, we considered four different Aß25-35 systems extracted from AD relevant fibril structures. From the calculation of different electron density properties, specific interacting loci were identified that guided the construction and optimization of various complexes. Interestingly, the results suggest a similar inhibitory mechanism based on the direct interaction between the AEs and the M35 residue that seems to be general and independent of the polymorphic properties of the Aß aggregates. Our analysis of the complex formation provides a structural framework for understanding the AE therapeutic properties in the molecular inhibitory mechanism of Aß aggregation.